This invention relates in general to preventing the production of particulate materials through a wellbore traversing an unconsolidated or loosely consolidated subterranean formation and, in particular, to an apparatus and method for obtaining a substantially complete gravel pack within an interval of the wellbore.
Without limiting the scope of the present invention, its background is described with reference to the production of hydrocarbon fluids through a wellbore traversing an unconsolidated or loosely consolidated formation, as an example.
It is well known in the subterranean well drilling and completion art that particulate materials such as sand may be produced during the production of hydrocarbons from a well traversing an unconsolidated or loosely consolidated subterranean formation. Numerous problems may occur as a result of the production of such particulate. For example, the particulate cause abrasive wear to components within the well, such as tubing, pumps and valves. In addition, the particulate may partially or fully clog the well creating the need for an expensive workover. Also, if the particulate matter is produced to the surface, it must be removed from the hydrocarbon fluids by processing equipment at the surface.
One method for preventing the production of such particulate material to the surface is gravel packing the well adjacent to the unconsolidated or loosely consolidated production interval. In a typical gravel pack completion, a sand control screen is lowered into the wellbore on a work string to a position proximate the desired production interval. A fluid slurry including a liquid carrier and a particulate material known as gravel is then pumped down the work string and into the well annulus formed between the sand control screen and the perforated well casing or open hole production zone.
The liquid carrier either flows into the formation or returns to the surface by flowing through the sand control screen or both. In either case, the gravel is deposited around the sand control screen to form a gravel pack, which is highly permeable to the flow of hydrocarbon fluids but blocks the flow of the particulate carried in the hydrocarbon fluids. As such, gravel packs can successfully prevent the problems associated with the production of particulate materials from the formation.
It has been found, however, that a complete gravel pack of the desired production interval is difficult to achieve particularly in long or inclined/horizontal production intervals. These incomplete packs are commonly a result of the liquid carrier entering a permeable portion of the production interval causing the gravel to form a sand bridge in the annulus. Thereafter, the sand bridge prevents the slurry from flowing to the remainder of the annulus which, in turn, prevents the placement of sufficient gravel in the remainder of the annulus.
Prior art devices and methods have been developed which attempt to overcome this sand bridge problem. For example, attempts have been made to use devices having perforated shunt tubes or bypass conduits that extend along the length of the sand control screen to provide an alternate path for the fluid slurry around the sand bridge.
It has been found, however, that shunt tubes installed on the exterior of sand control screens are susceptible to damage during installation and may fail during a gravel packing operation due, in part, to the perforations through the side wall of the shunt tubes. In addition, it has been found, that on site assembly of a shunt tube system around a sand control screen is difficult and time consuming due to the large number of fluid connections required for typical production intervals.
Therefore a need has arisen for an apparatus and method for gravel packing a production interval traversed by a wellbore that overcomes the problems created by sand bridges. A need has also arisen for such an apparatus that is not susceptible to damage during installation and will not fail during a gravel packing operation. Further, a need has arisen for such an apparatus that is cost effective and does not require difficult or time consuming on site assembly.
The present invention disclosed herein comprises an apparatus and method for gravel packing a production interval of a wellbore that traverses an unconsolidated or loosely consolidated formation that overcomes the problems created by the development of a sand bridge between a sand control screen and the wellbore. Importantly, the apparatus of the present invention is not susceptible to damage during installation or failure during the gravel packing operation, is cost effective to manufacture and does not require difficult or time consuming on site assembly.
The apparatus comprises a sand control screen that is positioned within the wellbore and a tube and manifold system that is positioned between the sand control screen and the wellbore. The tube and manifold system may be constructed in sections that are integral with each section of the sand control screen such that sections of the apparatus are simply threaded together in a known manner prior to running it downhole. Alternatively, the tube and manifold system may be run downhole and positioned proximate the formation prior to running the sand control screen downhole. In this case, when the sand control screen is run downhole, it is positioned within the tube and manifold system.
In either case, the tube and manifold system is used to selectively deliver the fluid slurry to a plurality of levels within the interval when the apparatus is in the operable position. The tube and manifold system comprises, in series, one or more tubes then a manifold followed by one or more tubes then another manifold and so forth. The tubes of the tube and manifold system have first and second ends which are open but do not have openings in their side walls as the fluid slurry is discharged from the tube and manifold system only through exit ports in the manifolds.
In most embodiments of the present invention, the exit ports of the manifolds are circumferentially misaligned with the adjacent tubes of the tube and manifold system. In other embodiment, however, some or all of the exit ports of the manifolds may be circumferentially aligned with the adjacent tubes of the tube and manifold system. There may be the same number, more or less exit ports in each manifold than the number of tubes delivering the fluid slurry to that manifold.
In one embodiment of the present invention, each section of the sand control screen has a plurality of manifolds positioned adjacently thereto. The tubes that deliver the fluid slurry to and transport the fluid slurry from these intrasectional manifolds are axially aligned with one another. In addition to these intrasectional manifolds, there is one manifold positioned between adjacent sections of the sand control screen. The tubes that deliver the fluid slurry to and transport the fluid slurry from these intersectional manifolds are typically axially misaligned with one another.
One method of the present invention involves traversing a formation with the wellbore, positioning a tube and manifold system within the wellbore proximate the formation, locating a sand control screen within the tube and manifold system, injecting a fluid slurry containing gravel through the tube and manifold system such that the fluid slurry exits the tube and manifold system through the exit ports in the manifolds at a plurality of levels of the interval and terminating the injecting when the interval is substantially completely packed with the gravel.
Another method of the present invention involves traversing a formation with the wellbore, positioning a tube and manifold system around a sand control screen, locating the sand control screen and the tube and manifold system within the wellbore proximate the formation, injecting a fluid slurry containing gravel through the tube and manifold system such that the fluid slurry exits the tube and manifold system through the exit ports in the manifolds at a plurality of levels of the interval and terminating the injecting when the interval is substantially completely packed with the gravel.